It's not THAT revolutionary, Olympus have had a 14-35mm F/2 for their DSLRs for a good while and that's unbelievably good quality. I know a professional press photographer who shoots Olympus specifically for that lens.

But it's the equivalent of a 28-70 f/4. A pretty mundane lens, wouldn't you say? The Sigma is the equivalent of a FF f/2.8 lens. That's a full stop extra in light gathering power.

I don't think Canon would invest their money in pursuing a lens like this, unless Nikon came out with one. I feel Canon would rather make more Rebels with no upgraded features than invest in their devoted/professional crop body shooters. Canon like to deal in extremes, ignorant amateur or needy professional.

APS format cameras are still the top-selling cameras in C and N's lineups. They really, really need to start making some professional grade lenses for these cameras.

I'm really excited about this lens, and I don't even own a crop body. I'm excited about the implications for the future. If this lens can be produced and has good optics (which will be the real issue), it raises so many interesting implications for the future.

A 27-55mm, or even 27-50mm f/1.8 FF lens would be absolutely amazing if it had good optics. Once the technology is out there, reverse engineering means that this advance will soon be in the hands of other manufacturers. The very nature of putting out an APS-C only lens means that the price has got to be somewhat reasonable, as there are not (to my knowledge) many APS-C lenses over a thousand dollars US.

That was kind of my thought: Wow lenses are starting to get really good! THey will most likely be getting a lot better here shortly!

Finally, a zoom better than f2.8. This is actually very exciting. I can see a 50-135 f1.8 coming down the pipeline one day.... And, my hands are now sweating for this and the fabled 7D MK II!!!

For video this does look nice. 15-40mm is the zoom everyone wants (while 18-85mm is the normal "prime" kit) so this fits in ok. A little wider would be nice. The speed is great, in fact about as fast as the fastest cinema zooms for super35.

REALLY nice to see an affordable WA/UWA for video, even ignoring the zoom. The fastest 16mm-18mm options were previously a stop and a half slower. That's big. Let's see how the image quality is. I compared the 17-55mm f2.8 IS (which I quite like) against the Angenieux Optimo 15-40mm t2.6 yesterday and the Canon doesn't even compare.

I think what has happened is that Canon's pricing policies have become SO absurd that is has given some astute tech. and money managers at Sigma the ability to realize that they have a lot more wiggle room to make a great product and still be super competitive in price to big read. (it also shows how ridiculous Canon's pricing has become). I do not own a crop body either, but I do LOVE the appearance of this lens! Hope the IQ and price/performance ratio are right up there with the Sigma 35mm, f/1.4 that I own and absolutely love. This can be nothing but good for all of us! Can't wait to see what the next lens is in the new Art Line!!!!!!!

I'm actually tremendously interested in a new version of their 24-70/2.8 and who knows, maybe something like a 24-90/4. The Tamron is quite good, but Sigma looks like they don't want to be a "second choice" anymore. I love when 3rd-party manufacturers deliver such quality; they set you free from this or that system.

This is great for crop shooters. However, before everyone gets excited over the f/1.8 bit, you have to remember that f/1.8 on a crop sensor is nothing like f/1.8 on a FF sensor. This lens will give the same angle of view, image noise for given exposure parameters (*1), depth of field at a given AOV and subject distance (*2), etc. etc. etc. as a 28-50mm f/2.8 full frame lens.

In other words, if the lenses and sensors are perfect, this lens on a crop sensor would give identical results to a 28-50mm f/2.8 on a FF sensor. However, lens and sensor imperfections actually favor the larger format sensor, so don't expect this lens to give anything as good as the 24-70 f/2.8 original or the tamron.

Still, its great improvement for crop shooters (if it keeps up with recent Sigma trends), and should be relatively compact.

(*1) This considers photon shot noise only and assumes photos are rescaled to same resolution when printed.(*2) At non-macro distances

Depending on the price point, the difference between a FF + 24-70 and DX + 18-35 might be what is truly impressive. This lens is not going to reach anything tremendous from an absolute perspective, but it's going to narrow the gap between crop and FF. Actually, I think it would make for an amazing travel lens since it would eliminate the need of a fast prime. If you want to travel light and bring only a crop body and one lens, you either go for a usual standard zoom and live with the slow aperture or you go with something like this.

3. What are the video implications of this lens? Surely there must be some (don't know since I don't video).

Well 1. has a huge impact on 3. No IS means that it wont be as useful for video as the 17-55 f2.8 IS.

- in order to get a stable and sharp single frame (from a rig/handheld) you really want Focal length x crop > shutter speed... So for stills IS isn't going to be much of an issue on a fast standard zoom. For video though, you're stuck with a shutter speed of 1/50th (1/60th in NTSC countries), And for video any movement between frames is also visible - hence why for video (if you aren't on a tripod/dolly/slider/crane) having IS is extremely useful.

I was flummoxed when I heard that this thing is APS-C only. Why?! If this is a premium lens aimed at serious shooters, why go crop? This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys? That would likely have a larger interest level.

- A

If I'm not mistaken, this has to do with technical & feasibility issues. Actual lens diameter for crop can be smaller than for ff bodies, thus making it easier to produce f/1.8. Or am I completely wrong right now?

You're not wrong, but for those saying this is no big deal, I disagree. This is something that has not been done before for either crop or FF (an f/1.8 zoom), so to dismiss it outright is absurd. Yes, developing for full frame is more challenging, but this is clearly a step in the right direction and will put more pressure on Canon. As a consumer, I see that as a good thing

Agreed that it's a big deal, as it's not been done before. But I don't think it makes it any more likely for full frame equivalent lens to be made, as that one would have to be larger.

Value is in closing the gap between APS-C and full frame, and if you're Nikon shooter, you have 27-52.5 f2.7 FF equivalent, for serious, but not FF money.

And as to why Sigma did this - I think they were looking for a gap where they can play by themselves for awhile. Crop sensor shooters looking for best/fastest glass they can get (in normal range) is probably not a huge market segment, but they own it now. And then there is a 'hallo' effect of 1.8, increasing value of their lineup. Smart play...

I'm pretty sure aperture is a fixed definition, doesn't matter if it's a compact P&S or medium format, the same numbers will give the same size lens (focal length divided by lens diameter = aperture) http://en.wikipedia.org/wiki/F-number

Compact cameras usually have a flange distance of close to nothing, a 3mm f2 would still be tiny, but with the extreme crop factor of compacts they make it seem like a normal camera.I just realized that it's probably the form factor of the camera that dictates the size of the sensor on those (the larger the sensor the larger the lenses, and thus the larger the camera would need to be).

"Aperture" is a word that is generally mis-used by the photographic community; people often say "aperture" where a pedantic person would say "f-stop". The aperture for a lens is measured in units of length (e.g. a 200mm f/4 lens has an aperture of 50mm). The "/" in "f/4" is actually a division sign, so instead of saying " an eff four lens" you should say "a lens with a maximum aperture equal to the focal length divided by four". Of course, if you said this, virtually noone would understand what you meant; and language is determined by common usage, much to the chagrin of us pedants

The aperture (here measured in millimeters) is, in general, not equal to the lens diameter. You can think of it in crude terms as the diameter of a pin-hole you would make in a pin-hole camera to gather the same amount of light as the subject lens gathers. However, for telephoto lenses, the maximum aperture (measured in millimeters, not f-stops) will typically be pretty close to the front element diameter. For normal or wide-angle lenses, that is not the case. (If you try to do the math yourself, note that the f-stop and focal length quoted by manufacturers are 'marketing numbers', not the real numbers.)

That said, it is a lot easier to make a "fast" (large aperture relative to focal length ) lens for smaller sensor cameras, e.g. 4/3 or P&S. However, larger format cameras seem to have the edge in terms of the actual aperture (measured in millimeters), and thus light gathering abilities, for a given angle of view. As I said before, this lens is about the equivalent of a f/2.8 FF lens, which is old-hat in the FF world.